[4] During the Civil War Barclay took part in the capture of the Confederate cruiser CSS Florida at Bahia, Brazil, by USS Wachusett in October 1864, and served on board the Kearsarge in 1865–66.

[4] Barclay recommissioned the monitor Amphitrite (BM-2) at Norfolk on 2 October 1897, commanding her during the Spanish–American War, and taking part in the bombardment of San Juan, Puerto Rico, on 12 May 1898, and then serving on blockade duty.

[6] He was the commandant of the Naval War Academy from 1900, and was therefore delegated captain of the Navy Yards at Boston and then at Puget Sound.

[2] Barclay was promoted to rear admiral on 20 November 1903,[7] and retired in 1905.

[2] He died of diabetes at his home in Brookline, Massachusetts, aged 66.